1. Field of the Invention
The present invention relates to a system and methodology for providing high- speed detection of faults in an AC power line by using phase-locking techniques to detect a power interruption or power degradation within a predetermined minimum time period.
2. Description of Related Art
Numerous power management systems exist which monitor an AC power line, and upon failure of the AC power, couple a battery backup system to a load. For example, U.S. Pat. No. 4,916,329 issued to Dang et al. discloses an uninterruptible power supply which monitors variations in a single AC power supply and decides, based on certain threshold limitations, whether to couple a backup battery supply to a load. Similar examples can be found in U.S. Pat. Nos. 5,790,391; 5,670,833; 5,602,462; and 4,916,329.
However, in certain applications, it is impractical to design a redundant power supply system based on a battery backup system since some loads will quickly deplete a battery. Such implementations require one or more redundant AC power lines to provide continuous power to the load. Thus, there is a need to provide a control system for controlling a power line selection to a load. There also exists a need to provide a detection mechanism which can detect a failed power line within a minimum time frame so that a redundant power line can be quickly applied to a load. Also, since certain load elements are sensitive to AC power voltage variations, for example, brownout conditions and/or spike conditions, there exists a need to detect such conditions on a given power line, and if such condition exists, couple a redundant power line to the load.
Accordingly, the present invention solves the drawbacks of prior art redundant AC power supply systems by providing a detection system that monitors multiple AC power lines to ensure that the most viable AC power line is coupled to the load. Additionally, the present invention solves other drawbacks of prior art redundant AC power systems by providing threshold detection circuitry to monitor the signal condition of multiple AC power lines so that the power line connected to the load meets certain predetermined threshold conditions.
In one embodiment, the present invention provides a signal detection system, comprising an input AC signal; a trigger circuit receiving said AC signal and generating a digital signal;
a phase lock loop circuit receiving said digital signal and generating a phased digital signal such that said phased digital signal and said digital signal have overlapping values when said AC signal is present; and a latch circuit receiving said digital signal and said phased digital signal and latching said digital signal based on said phased digital signal, said latch circuit generating a detection signal indicative of the presence of said AC signal if said digital signal remains latched.
In another embodiment, the present invention provides an AC power line detection system to detect interruption of AC power, comprising an input AC signal; a trigger circuit receiving said AC signal and generating a digital signal; a phase lock loop circuit receiving said digital signal and generating a phased digital signal; a threshold detection circuit receiving said AC input signal and comparing said AC signal with a voltage threshold, and generating a second digital signal indicative of the presence and condition of said AC signal; and a latch circuit receiving said second digital signal and said phased digital signal and latching said second digital signal based on said phased digital signal, said latch circuit generating a detection signal indicative of the presence of said AC signal if said digital signal remains latched.
In still other system-level embodiments, the present invention provides a redundant power supply system.adapted to detect power interruption of a redundant AC power line comprising: a plurality of available AC power signals; a reference signal generator circuit receiving a selected AC signal and generating a phased signal based on said AC signal; a detection circuit comparing said phased signal with said AC signal and generating a signal indicative of the presence of said AC signal; a switch controller receiving said- signal indicative of the presence of said AC signal and generating a control signal; and a switch array receiving said control signal and coupling said AC signal to a load if said AC signal is present.
It will be appreciated by those skilled in the art that although the following Detailed Description will proceed with reference being made to preferred embodiments and methods of use, the present invention is not intended to be limited to these preferred embodiments and methods of use. Rather, the present invention is of broad scope and is intended to be limited as only set forth in the accompanying claims.
Other features and advantages of the present invention will become apparent as the following Detailed Description proceeds, and upon reference to the Drawings, wherein like numerals depict like parts, and wherein: